Henri Hänninen

Henri Hänninen

he/him

Postdoctoral researcher at University of Jyväskylä, expert in theoretical particle physics and working on applying inverse problems to contemporary high-energy physics

Publications

You can also find my articles on iNspire HEP and Google Scholar.

Peer-reviewed Journal Articles

Proton Structure Functions at Next-to-Leading Order in the Dipole Picture with Massive Quarks

Published in Physical Review Letters, 2022

We predict heavy quark production cross sections in deep inelastic scattering at high energy by applying the color glass condensate effective theory. We demonstrate that, when the calculation is performed consistently at next-to-leading order accuracy with massive quarks, it becomes possible, for the first time in the dipole picture with perturbatively calculated center-of-mass energy evolution, to simultaneously describe both the light and heavy quark production data at small xBj. Furthermore, we show how the heavy quark cross section data provides additional strong constraints on the extracted nonperturbative initial condition for the small-xBj evolution equations.

Recommended citation: H. Hänninen, H. Mäntysaari, R. Paatelainen, J. Penttala. (2022). "Proton Structure Functions at Next-to-Leading Order in the Dipole Picture with Massive Quarks" Phys.Rev.Lett. 130 (2023) 19, 19.
Download Paper

Diffractive deep inelastic scattering at NLO in the dipole picture: The qqg contribution

Published in Phys.Rev.D 106 9, 094014, 2022

We calculate the contribution from the qq¯g state production to the diffractive cross sections in deep inelastic scattering at high energy. The obtained cross section is finite by itself and a part of the full next-to-leading order result for the diffractive structure functions. We perform the calculation in exact kinematics in the eikonal limit, and show that the previously known high-Q2 and large M_X2 results for the structure functions can be extracted from our results in the appropriate limits. We furthermore discuss the steps required to obtain the full next-to-leading order results for the structure functions.

Recommended citation: G. Beuf, H. Hänninen, T. Lappi, Y. Mulian, H. Mäntysaari. (2022). "Diffractive deep inelastic scattering at NLO in the dipole picture: The qqg contribution", Phys.Rev.D. 106 (2022) 9, 094014.
Download Paper

Color Glass Condensate at next-to-leading order meets HERA data

Published in Phys.Rev.D 102 074028, 2020

We perform the first dipole picture fit to HERA inclusive cross section data using the full next-to-leading order (NLO) impact factor combined with an improved Balitsky-Kovchegov evolution including the dominant effects beyond leading logarithmic accuracy at low x. We find that three different formulations of the evolution equation that have been proposed in the recent literature result in a very similar description of HERA data, and robust predictions for future deep inelastic scattering experiments. We find evidence pointing towards a significant nonperturbative contribution to the structure function for light quarks, which stresses the need to extend the NLO impact factor calculation to massive quarks.

Recommended citation: G. Beuf, H. Hänninen, T. Lappi, H. Mäntysaari. (2020). "Color Glass Condensate at next-to-leading order meets HERA data", Phys.Rev.D. 102 (2020) 074028.
Download Paper

One-loop corrections to light cone wave functions: the dipole picture DIS cross section

Published in Annals Phys. 393, 358-412, 2017

We develop methods to perform loop calculations in light cone perturbation theory using a helicity basis, refining the method introduced in our earlier work. In particular this includes implementing a consistent way to contract the four-dimensional tensor structures from the helicity vectors with d -dimensional tensors arising from loop integrals, in a way that can be fully automatized. We demonstrate this explicitly by calculating the one-loop correction to the virtual photon to quark–antiquark dipole light cone wave function. This allows us to calculate the deep inelastic scattering cross section in the dipole formalism to next-to-leading order accuracy. Our results, obtained using the four dimensional helicity scheme, agree with the recent calculation by Beuf using conventional dimensional regularization, confirming the regularization scheme independence of this cross section.

Recommended citation: H. Hänninen, T. Lappi, R. Paatelainen. (2018). "Annals of Physics" Volume 393 358-412.
Download Paper

Deep inelastic scattering in the dipole picture at next-to-leading order

Published in Phys. Rev. D 96, 094017, 2017

We study quantitatively the importance of the recently derived NLO corrections to the DIS structure functions at small x in the dipole formalism. We show that these corrections can be significant and depend on the factorization scheme used to resum large logarithms of energy into renormalization group evolution with the BK equation. This feature is similar to what has recently been observed for single inclusive forward hadron production. Using a factorization scheme consistent with the one recently proposed for the single inclusive cross section, we show that it is possible to obtain meaningful results for the DIS cross sections.

Recommended citation: B. Ducloué, H. Hänninen, T. Lappi, Y. Zhu. (2017). "Deep inelastic scattering in the dipole picture at next-to-leading order" Phys. Rev. D. 96, 094017 (2017).
Download Paper

Thesis

Deep inelastic scattering in the dipole picture at next-to-leading order

Published in JYX, 2021

This thesis studies gluon saturation in hadronic matter at high energy by calculating next-to-leading order (NLO) corrections to inclusive and diffractive deep inelastic scattering cross sections in the Color Glass Condensate (CGC) effective field theory. We demonstrate that the large soft gluon logarithm is correctly factorized into the Balitsky–Kovchegov (BK) renormalization group equation by accurately connecting the NLO scattering kinematics to the rapidity scale of the dipole amplitude in the scattering. This brings the perturbative expansion under control and enables us to do precision comparisons between theory and data. We fit the initial condition of the BK evolution equation to HERA inclusive deep inelastic scattering data by combining of the NLO accuracy inclusive cross sections with beyond leading order BK evolution prescriptions. This results in the state-of-the- art accuracy comparison between CGC theory and HERA data, and determination of the dipole amplitude initial shape which is a necessary input for all NLO CGC phenomenology.

Recommended citation: H. Hänninen. (2021). "Deep inelastic scattering in the dipole picture at next-to-leading order" PhD thesis, Jyväskylä U.
Download Paper

Conference Proceedings

Proton structure functions in the dipole picture at next-to-leading order

Published in DIS2023 Proceedings, 2023

We predict heavy quark production cross sections in Deep Inelastic Scattering at high energy by applying the CGC effective theory. We demonstrate that when the calculation is performed consistently at next-to-leading order accuracy with massive quarks it becomes possible, for the first time in the dipole picture with perturbatively calculated center-of-mass energy evolution, to simultaneously describe both light and heavy quark production data at small xx. We furthermore show how the heavy quark cross section data provides additional strong constraints on the extracted non-perturbative initial condition for the small-x evolution equations.

Recommended citation: G. Beuf, H. Hänninen, T. Lappi, Y. Mulian, H. Mäntysaari. (2023). "Diffractive Deep Inelastic Scattering in the Dipole Picture at Next-to-Leading Order" DIS2023. e-Print: 2307.06321 [hep-ph].
Download Paper

Proton structure functions in the dipole picture at next-to-leading order

Published in DIS2023 Proceedings, 2023

We predict heavy quark production cross sections in Deep Inelastic Scattering at high energy by applying the CGC effective theory. We demonstrate that when the calculation is performed consistently at next-to-leading order accuracy with massive quarks it becomes possible, for the first time in the dipole picture with perturbatively calculated center-of-mass energy evolution, to simultaneously describe both light and heavy quark production data at small xx. We furthermore show how the heavy quark cross section data provides additional strong constraints on the extracted non-perturbative initial condition for the small-x evolution equations.

Recommended citation: H. Hänninen, H. Mäntysaari, R. Paatelainen, J. Penttala. (2023). "Proton structure functions in the dipole picture at next-to-leading order" DIS2023. e-Print: 2306.17707 [hep-ph].
Download Paper

Diffractive Structure Function in the Dipole Picture

Published in Difflowx2022, 2023

We calculate the contribution from the qqbarg component of a virtual photon state to the small-x diffractive cross section in deep inelastic scattering in the saturation regime. The obtained cross section is finite by itself and a part of the full next-to-leading order result. We perform the calculation in exact kinematics in the eikonal limit, and show that the previously known high virtuality Q2 and large invariant mass M_X2 results for the structure functions can be extracted. We furthermore discuss the steps required to obtain the full next-to-leading order result.

Recommended citation: G. Beuf, H. Hänninen, T. Lappi, Y. Mulian, H. Mäntysaari. (2023). "Diffractive Structure Function in the Dipole Picture" Acta Phys.Polon.Supp. 16 (2023) 5, 20.
Download Paper

Dipole model at Next-to-Leading Order meets HERA data

Published in HardProbes2020, 2020

Deep inelastic scattering (DIS) total cross section data at small-x as measured by the HERA experiments is well described by Balitsky-Kovchegov (BK) evolution in the leading order dipole picture. Recently the full Next-to-Leading Order (NLO) dipole picture total cross sections have become available for DIS, and a working factorization scheme has been devised which subtracts the soft gluon divergence present at NLO. We report our recently published work in which we make the first comparisons of the NLO DIS total cross sections to HERA data. The non-perturbative initial condition to BK evolution is fixed by fitting the HERA reduced cross section data. As the NLO results for the DIS total cross section are currently available only in the massless quark limit, we also fit a light-quark-only cross section constructed with a parametrization of published total and heavy quark data. We find an excellent description of the HERA data. Since the full NLO BK equation is computationally expensive, we use a number of beyond LO prescriptions for the evolution that include most important higher order corrections enhanced by large transverse logarithms, including the recent version of the equation formulated in terms of the target momentum fraction.

Recommended citation: G. Beuf, H. Hänninen, T. Lappi, H. Mäntysaari. (2021). "Dipole model at Next-to-Leading Order meets HERA data" PoS HardProbes2020 (2021) 101.
Download Paper

Factorization of the soft gluon divergence from the dipole picture deep inelastic scattering cross sections at next-to-leading order

Published in DIS2018, 2018

We use a factorization scheme analogous to one proposed for single inclusive forward hadron production to factorize the soft gluon divergence present in the deep inelastic scattering cross sections in the dipole picture at next-to-leading order (NLO). We show numerically that in this carefully constructed scheme it is possible to obtain meaningful results for the DIS cross sections at NLO, and so we are able to quantitatively study the recently derived NLO corrections to the DIS cross sections. We find that the NLO corrections can be significant and sensitive to the details of the factorization scheme used for the resummation of the large logarithms into the BK evolution equation. In the case of an approximative factorization scheme we observe a problematic behavior of the DIS cross sections similar to what has been seen with analogously factorized single inclusive cross sections.

Recommended citation: B. Ducloué, H. Hänninen, T. Lappi, Y. Zhu. (2017). "Factorization of the soft gluon divergence from the dipole picture deep inelastic scattering cross sections at next-to-leading order" PoS. DIS2018 (2018) 058.
Download Paper